Call Service Fall Back (CSFB) is a technology used by LTE (Long Term Evolution) to provide voice service, by instructing a terminal to fall back from an LTE network to a 2G or 3G network. The called terminal makes a response after receiving a call request sent by an MME (Mobility Management Entity), the MME in cooperation with an MSC (Mobile Switching Center) instructs the terminal to fall back to a 2G or 3G network through eNB, and then the terminal carries out a voice call setup procedure on the 2G or 3G network.
In a traditional CSFB solution, immediately after receiving the call request, the terminal falls back to the 2G or 3G network to start a call setup procedure and receive OTA (Over-the-Air technology) messages such as SETUP (update) information. It is only through the SETUP information that the called terminal is able to know the calling party, and even if the terminal does not want to answer this call, because the terminal has already fallen back to the 2G or 3G network with a smaller bandwidth, the data service running on LTE, such as video call service, has already been affected or directly interrupted.
Therefore, a new technical solution is needed, which can determine whether to carry out a circuit domain fallback according to whether a user answers a call, so that the data service is not affected when the user does not answer the call, thereby improving user experience.